The treatment of otitis media provides for a tubular ventilation device to be surgically implanted in the tympanic membrane to balance a pressure difference established between the middle ear and the outer ear. At one time such implants had to be surgically removed at the end of the treatment. Nowadays there have been devised, but hitherto never produced on an industrial scale, devices produced from biodegradable materials, such as polylactides, subject to biological degradation in the presence of organic liquids. An example of such devices (otherwise known as reabsorbable auricular ventilation tubes) is described in U.S. Pat. No. 4,650,488. The device described therein has a tapered body, of substantially frustoconical configuration, traversed axially by a hole and having a flanged end at the minor base. The device, or at least the flanged portion thereof, is produced from a biodegradable material based on polymers of lactic acid. Such a device has not hitherto been applied in the field inasmuch as it is potentially susceptible to exposing the patients in which it is implanted to numerous risks. Firstly, the polylactides involve the risk of growth of granulation tissues consequent upon their imperfect absorption by the tissues. The formation of granulation tissues is particularly risky in auricular treatments.
Moreover, both through the typical degradation of the material used and through the frustoconical configuration of the tapered body it involves the risk that the epithelial growth with which the hole for application of the prosthesis tends to close itself up again develops with invagination of the keratinized squamous epithelium, of the actual outer ear, along the conical portion and towards the middle ear, where mucous epithelium is present. There is in practice a risk of migration of the keratinized squamous epithelium towards the middle ear which is a possible cause of cholesteatoma.
All the problems in question have hitherto led to delays in the marketing of devices of the aforesaid type. Moreover, up to now there have not been reabsorbable auricular ventilation tubes approved by the FDA (Federal Drug Administration) of the United States.